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| United States Patent |
6,026,207
|
|
Reddy
, et al.
|
February 15, 2000
|
Black appearing color coating for optical fiber and method using same
Abstract
A non-carbon black pigment blend is mixed with a coating layer of an
optical fiber to provide a black appearing colored optical fiber. The
pigment blend does not absorb UV light and is formed by blending three
primary colors including red, blue and yellow. The combination of these
three primary colors creates a black appearing colored secondary coating.
The proportions of the primary colors are controlled to provide the
desired shade of black with, in general, no one coloration of pigment
exceeding 45% by weight of the total pigment added to the secondary
coating. The pigment blend may further include white pigment to provide a
slate tone black appearing color. The proportion of white pigment, in
general, not exceeding 10 percent by weight of the total pigment added to
the secondary coating. The pigment is mixed as a concentrate which is
added to a secondary coating layer for application to the optical fiber.
Typically, the pigment concentrate is premixed with the secondary coating
layer; however, the pigment may also be directly combined with the
secondary coating material during application to the optical fiber. The
optical fiber may include one or more secondary coating layers, with the
pigment concentrate being combined with the outermost secondary coating
layer on the optical fiber.
| Inventors:
|
Reddy; Srinath S. (Cornelius, NC);
Auton; Jeffrey W. (Maiden, NC);
Overton; Bob J. (Lenoir, NC)
|
| Assignee:
|
Alcatel (FR)
|
| Appl. No.:
|
859933 |
| Filed:
|
May 21, 1997 |
| Current U.S. Class: |
385/128; 385/123; 385/127; 385/141; 427/162; 427/163.2 |
| Intern'l Class: |
G02B 006/02; B05D 005/06 |
| Field of Search: |
385/100,123,126,127,128,141
427/162,163.2
|
References Cited
U.S. Patent Documents
| 3742107 | Jun., 1973 | Hawkins | 264/174.
|
| 4482204 | Nov., 1984 | Blyler, Jr. et al. | 385/128.
|
| 4629285 | Dec., 1986 | Carter et al. | 385/128.
|
| 4900126 | Feb., 1990 | Jackson et al. | 385/128.
|
| 5062685 | Nov., 1991 | Cain et al. | 385/128.
|
| 5062687 | Nov., 1991 | Sapsford | 385/128.
|
| 5074643 | Dec., 1991 | Petisce | 385/128.
|
| 5111523 | May., 1992 | Ferlier et al. | 385/100.
|
| 5146529 | Sep., 1992 | Mizutani | 385/103.
|
| 5151306 | Sep., 1992 | Andrews et al. | 427/434.
|
| 5152817 | Oct., 1992 | Bennett et al. | 385/128.
|
| 5164999 | Nov., 1992 | Shifflett | 385/12.
|
| 5259060 | Nov., 1993 | Edward et al. | 385/128.
|
| 5377292 | Dec., 1994 | Bartling et al. | 385/128.
|
| 5381505 | Jan., 1995 | Fischietto et al. | 385/128.
|
| 5446821 | Aug., 1995 | Nonaka et al. | 385/128.
|
| 5796905 | Aug., 1998 | Hoffart et al. | 385/128.
|
| Foreign Patent Documents |
| 0155092 | Sep., 1985 | EP | 385/128.
|
| 0411310 | Feb., 1991 | EP | 385/128.
|
| 0501339 | Sep., 1992 | EP | 385/128.
|
| 8909842 | Nov., 1989 | DE | 385/128.
|
Other References
"EIA Standard Colors for Color Identification and Coding," Electronic
Industries Association, Jan. 1985, pp. 1-14.
EIA/TIA Standard Color Coding of Fiber Optic Cables, Electronic Industries
Association, Apr. 1992, pp. 1-10.
"Operating Instructions for Fusion Splicer M90/Series 3000," Siecor, Feb.
1995, pp. 1-1 to 1-10.
|
Primary Examiner: Healy; Brian
Attorney, Agent or Firm: Ware, Fressola, Van der Sluys & Adolphson LLP
Claims
What is claimed is:
1. A pigment concentrate for combination with an outermost coating layer of
an optical fiber for producing a black appearing colored optical fiber,
comprising:
a blend of primary color pigment concentrates including red pigment
concentrate, blue pigment concentrate and yellow pigment concentrate;
wherein no carbon-black pigment is included in said blend of primary color
pigment concentrates; and
wherein said primary color pigment concentrates are selected such that said
blend of primary color pigment concentrates added to the outermost coating
of an optical fiber does not absorb ultra-violet light.
2. The pigment concentrate of claim 1, wherein no one primary color pigment
concentrate exceeds 45% by weight of said blend of primary color pigment
concentrates.
3. The pigment concentrate of claim 2, further comprising a white pigment
concentrate.
4. The pigment concentrate of claim 3, wherein said white pigment
concentrate does not exceed 10% by weight of said blend of primary color
pigment concentrates.
5. A method for forming an optical fiber having a black appearing
coloration including the steps of:
providing an outermost coating layer to be applied to the optical fiber;
providing a blend of primary color pigment concentrates including red
pigment concentrate, blue pigment concentrate and yellow pigment
concentrate, wherein no carbon-black pigment is included in the pigment
concentrate;
selecting said primary color pigment concentrates such that said blend of
pigment concentrates does not absorb ultra-violet light;
combining said blend of primary color pigment concentrates with the
outermost coating layer prior to application of the outermost coating
layer to the optical fiber; and
applying the combined outermost coating layer and blend of primary color
pigment concentrates to the optical fiber.
6. The method of claim 5, further including the step of combining said
primary color concentrates to form said blend of primary color pigment
concentrates such that no one primary color pigment concentrate exceeds
45% by weight of said blend of primary color pigment concentrates.
7. The method of claim 6, further including the step of blending a white
pigment concentrate with said blend of primary color pigment concentrates.
8. The method of claim 7, wherein said white pigment concentrate does not
exceed 10% by weight of said blend of primary color pigment concentrates.
9. A black appearing color coating layer for an optical fiber, comprising:
a coating material for providing a coating layer on an optical fiber;
a blend of primary color pigment concentrates which is added to said
coating material, the combination of said coating material and said blend
of primary color pigments forming a black appearing color coating for an
optical fiber;
wherein no carbon-black pigment is included in said blend of primary color
pigment concentrates; and
wherein said primary color pigment concentrates are selected such that said
blend of primary color pigment concentrates does not absorb ultra-violet
light.
10. A black appearing color coating layer for an optical fiber as claimed
in claim 9, wherein said blend of primary color pigment concentrates
includes red pigment concentrate, blue pigment concentrate and yellow
pigment concentrate.
11. A black appearing color coating layer for an optical fiber as claimed
in claim 10, wherein no one primary color pigment concentrate exceeds 45%
by weight of said blend of primary color pigment concentrates.
12. A black appearing color coating layer for an optical fiber as claimed
in claim 11, wherein said primary color pigment concentrate further
includes a white pigment concentrate.
13. A black appearing color coating layer for an optical fiber as claimed
in claim 12, wherein said white pigment concentrate does not exceed 10% by
weight of said primary color pigment concentrate.
Description
TECHNICAL FIELD
The present invention relates to optical fibers, and more particularly to
coloration of optical fibers for identification of individual optical
fibers.
BACKGROUND OF THE INVENTION
Optical fiber cables containing a plurality of optical fibers for the
transmission of optical signals are well known. Such optical fiber cables
typically include a core which may have a strength member to carry the
axial tensile stress and axial compressive forces on the cable. Also
located within the core are one or more tubes. Each tube typically
includes a plurality of optical fibers. The optical fibers within a tube
may be individually stranded or may be provided in an optical fiber
ribbon. A sheath is provided to enclose the core including the tubes and
the strength member. The optical fibers included within such a cable
typically include a glass core and one or more claddings and/or coatings.
During a process of manufacturing a glass optical fiber, a glass fiber is
drawn from a preform and then coated with one or more coating materials,
typically ultra-violet light curable materials. The coating materials
include, for example, polymeric compositions and are applied by one or
more coating applicators. The function of the fiber coating is to protect
the surface of the glass optical fiber from mechanical scratches and
abrasions which the optical fiber may experience during subsequent
handling and use. The coating or coatings also influence the fiber's
optical characteristics in response to external mechanical forces and
environmental temperature.
Optical fibers are almost universally color-coded in their end use. There
are numerous colors which are acceptable in most markets, with additional
identification being made possible by "banding" colored fibers with
additional colors or circumferential striping. One well-known method of
coloring an optical fiber is to apply an ink layer to an optical fiber
having single or dual coating layers so that the total composite optical
fiber includes primary and secondary coating layers with an outermost ink
layer. The ink coloring layer is thin, typically 3 to 5 microns in
thickness, and typically includes a carrier resin and a pigment system.
The carrier resin may typically be a soluble thermoplastic material or a
ultra-violet (UV) curable resin. In the former, the ink is applied via a
dye or a transfer method, such as a felt-tip applicator or roller, and the
solvent for the carrier resin is driven off by heat to leave the pigmented
resin on the fiber. In the UV system, there is no solvent. The liquid
resin pigment is cured to a solid state by UV energy. Either ink involves
a separate step from either optical fiber production or the cabling
operation.
An alternative method for color-coding the fiber is to have the color mixed
directly into a secondary (outer) coating of a dual coated optical fiber.
The secondary coating acts as the carrier resin for the coloring agents.
One desirable color used for optical fiber coloration is black, and also
slate-colored derivations thereof. It is well known in the art to use
carbon based black pigment blends in a coloring layer over a fiber having
single or dual coating layers to obtain a black or slate color for
identification of the optical fiber within a telecommunications cable or
ribbon. However, there are several problems associated with using such a
carbon based black pigment coloring layer. First, the carbon material
absorbs light in the UV region. This presents a potentially significant
problem if the primary and secondary coating layers are made of a UV
curable material which is not completely cured prior to the application of
the color layer. The absorption of UV light by the color layer inhibits a
complete cure of the coatings on the optical fiber during drawing of the
optical fiber.
A second problem associated with the use of a carbon based black color
layer is that the absorption of light by the carbon in the color layer
inhibits the use of optical fiber fusion splicing equipment. One
well-known method of fusing two lengths of optical fiber is to use a fuse
and splice apparatus which automatically aligns and splices two lengths of
optical fiber. With the automatic alignment, two lengths of optical fiber
to be spliced are bent, for example about a mandril, on either side of the
intended splice location. Light is injected into one of the fibers at the
location of the bend. The injected light passes through the splice
location and is detected at the bend location of the second fiber. The
device aligns the fibers for fusion at the splice by determining the
alignment of the optical fibers for maximum light transmission. The
problem associated with using the carbon black coloring for optical fibers
is that the carbon absorbs the injection light, which is typically
injected at a wavelength of approximately 1300 nm. This light absorption
by the carbon black coloring results in a very weak signal, or no signal,
being passed through the fiber for purposes of alignment, thereby
aggravating the problems associated with aligning and fusion splicing
fibers.
The carbon black coloring materials currently used in the industry are
selected to meet the tolerances specified for color distinguishability in
industry standards, such as the standards established by the Electronic
Industries Association, EIA/TIA-359-A entitled EIA Standard Colors for
Color Identification and Coding, January, 1985 and in EIA/TIA-598 entitled
Color Coding of Fiber Optic Cables, April 1992. It would be desirable to
provide a black appearing coloration for an optical fiber which meets
industry requirements for color distinguishability and which does not
absorb UV light, thereby allowing the black colored appearing optical
fiber to properly cure and to operate with a fusion splicing device which
utilizes automatic alignment of fibers by launching UV light into the
optical fibers.
SUMMARY OF THE INVENTION
Objects of the invention include a black appearing coloration for an
optical fiber, the black appearing coloration being integral with a
secondary coating layer of the optical fiber, which does not absorb UV
light, thereby allowing for UV curing of primary and secondary coating
layers which is not inhibited by the black appearing coloration in the
secondary coating layer, and also allowing alignment of segments of
optical fiber having the black appearing coloration by injecting light
into a side of the fiber.
Another object of the invention is to provide such a black appearing
coloration for an optical fiber which meets industry requirements for
color distinguishability.
According to the present invention, a non-carbon black pigment blend which
does not absorb UV light is formed by blending three primary colors
including red, blue and yellow. The combination of these three primary
colors creates a black appearing colored secondary coating. The
proportions of the primary colors are controlled to provide the desired
shade of black with, in general, no one coloration of pigment exceeding
45% by weight of the total pigment added to the secondary coating.
In further accord with the invention, the pigment blend may further include
white pigment to provide a slate tone black color. The proportion of white
pigment, in general, not exceeding 10 percent by weight of the total
pigment added to the secondary coating.
In still further accord with the present invention, the pigment is mixed as
a concentrate which is added to a secondary coating layer for application
to the optical fiber. Typically, the pigment concentrate is premixed with
the secondary coating layer; however, the pigment may also be directly
combined with the secondary coating material during application to the
optical fiber.
According further to the present invention, the optical fiber may include
one or more secondary coating layers, with the pigment concentrate being
combined with the outermost secondary coating layer on the optical fiber.
The present invention provides a significant improvement over the prior
art. Firstly, a black appearing coloration for an optical fiber is
provided which does not absorb UV light. Therefore, the coloration does
not inhibit curing of primary and secondary coating layers on an optical
fiber if the coloration is applied prior to complete curing of the primary
and secondary coatings. Additionally, because the coloration does not
absorb UV light, the coloration does not inhibit the alignment of
different lengths of optical fiber having the black appearing coloration
for fusion splicing by injection of UV light into the optical fiber. A
further advantage of the present invention is provided by including the
coloration directly in a secondary coating on the optical fiber as opposed
to providing a separate color layer on the optical fiber after curing the
primary and secondary coatings. Therefore, the manufacturing of the
optical fiber is simplified by removing a step, thereby facilitating a
more economical production of a black color appearing optical fiber.
The foregoing and other objects, features and advantages of the present
invention will become more apparent in light of the following detailed
description of exemplary embodiments thereof, as illustrated in the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic block diagram of a draw tower used to produce an
optical fiber in accordance with the present invention; and
FIG. 2 is a cross-sectional view of an optical fiber having a primary
cladding and a black colored secondary cladding of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is particularly well suited for providing a black
appearing coloration for an optical fiber without the need for using a
carbon-black pigment coloration in order to achieve the desired black
appearing coloration. As is well known in the art, carbon-black pigment is
typically used to produce a black colored optical fiber. Carbon-black
pigment is a carbon based pigment concentrate which is well known in the
industry for providing a black coloration for an optical fiber. The black
appearing coloration of the present invention is provided by including a
non-carbon-black pigment concentrate in a secondary coating layer of the
optical fiber. The coloration does not inhibit curing of the coating
layers on the optical fiber and also does not preclude the injection of
light through a side of the fiber for purposes of alignment and splicing.
As used herein, the terms "black appearing coloration," "black appearing
color" and like phrases are intended to include both black and
slate-colored derivations thereof (slate-black). The black appearing
coloration of the invention meets industry requirements for color
distinguishability.
Referring to FIG. 1, a schematic block diagram showing a typical draw tower
is provided. The draw tower is usually a vertical arrangement wherein a
preform (not shown) is introduced into a furnace 10 such that an optical
fiber can be drawn from a heated end of the preform. The composition of
the preform will largely depend upon the type of optical fiber desired
(single mode, multimode, dispersion shifted, etc.) After exiting the
furnace, the optical fiber may be passed through measuring devices 12
which may measure the diameter and the tension of the optical fiber being
drawn from the preform. Next the optical fiber passes through a primary
coating apparatus 15, such as a coating die, wherein a coating is applied
to the optical fiber. The coating may be a UV curable resin, a
thermosetting resin, a radiation curable resin, or other suitable coating
known in the art for providing the desired mechanical properties to the
surface of the optical fiber. After exiting the primary coating device 15,
the optical fiber enters a curing stage 17 wherein the primary coating is
at least partially cured. For example, if the primary coating is a UV
curable coating, the curing stage 15 includes a UV light source for
exposing the primary coating to UV light for curing the primary coating.
Alternatively, if the primary coating is a thermosetting resin, the
primary coating is exposed to a heat source. As will be understood by
those skilled in the art, the curing stage 15 will provide the desired
environment or conditions for curing of the primary coating.
Typically, optical fibers are provided with at least two coating layers.
Each coating layer is selected to have certain desirable mechanical
properties. The primary coating is typically selected to have a relatively
low Young's modulus to provide cushioning support for the fiber and to act
as a buffer or shock absorber. The secondary coating layer is selected to
have a higher Young's modulus to provide a hard protective layer for the
complete fiber.
After exiting the first curing stage 17, the optical fiber coated with the
primary coating is provided to additional coating and curing stages 20, 21
respectively wherein one or more secondary coatings are added to the
fiber. After the final cure stage, the coated optical fiber may be passed
through a measuring device 30 wherein the final outside diameter of the
coated optical fiber is measured. Finally, the coated optical fiber is
provided to a tensioning and drawing device 32 wherein the coated optical
fiber is drawn out of the drawing tower and provided to a take up spool
(not shown). The coated optical fiber may pass over one or more pulleys
before being provided to the take up spool. The tensioning and drawing of
the optical fiber may be accomplished in a suitable way known in the art,
such as is disclosed in commonly owned, copending patent application Ser.
No. 08/588,974, filed on Jan. 19, 1996, the disclosure of which is
incorporated herein by reference, with particular reference to FIG. 2 and
the accompanying description.
In accordance with the present invention, the outermost secondary coating
is mixed with a pigment concentrate, which includes a combination of
pigments, to provide the black appearing colored optical fiber of the
invention. In particular, the entire secondary coating layer is pigmented
with a combination of pigments to provide a black appearing colored
secondary coating. Several shades of black, ranging from a slate-black
color to a deep purplish black color can be achieved, depending on the
relative proportions and the type of pigment used to form the pigment
concentrate.
Several fibers having a black appearing color where achieved by combining
red, blue, yellow and white pigment in a concentrate and premixing this
pigment concentrate with the secondary coating prior application of the
secondary coating to the optical fiber. The pigments were selected to be
organic pigment material well known in the art having a typical particle
size of less then 2 microns, with the maximum size of any particle being
less than 5 microns. Organic base pigments were selected such that the
pigment is not susceptible to bleeding or migration when exposed to
filling and flooding compounds utilized in optical fiber cables. As is
know in the art, such filling and flooding compounds are used as water
blocking agents within optical fibers and come in direct contact with the
surface of the optical fibers within an optical fiber cable. The amount of
pigment added to the secondary coating is selected to provide the desired
final black appearing color. Typically, the pigment concentrate makes up
between about 0.10% to 5% of the total secondary coating material after
premixing of the pigment concentrate with the secondary coating, depending
upon the final color desired.
Several examples of pigment concentrate combinations found to be suitable
for use as a black appearing coloration for secondary coatings of an
optical fiber are listed in Table II below:
TABLE II
______________________________________
PIGMENT CONCENTRATE EXAMPLES
% RED % BLUE % YELLOW
% WHITE
EXAMPLE PIGMENT PIGMENT PIGMENT PIGMENT
______________________________________
EXAMPLE 1
38 32 30 0
PURPLISH
BLACK
EXAMPLE 2
36 34 30 0
BROWNISH
BLACK
EXAMPLE 3
39 34 27 0
BLACK
EXAMPLE 4
38 32 30 0
SLATE
(DARK)
EXAMPLE 5
33.5 32 33 0.5
SLATE
EXAMPLE 6
34 32 33 1
SLATE
EXAMPLE 7
36 31 30 3
SLATE
(LIGHT)
______________________________________
In general, the percentage of each pigment should meet the following guide
line: .ltoreq.45% red; .ltoreq.45% blue; .ltoreq.45% yellow; .ltoreq.10%
white. The visually perceived shade of chromatic black and slate will vary
according to the percentage of each pigment used in the pigment
concentrate.
The pigment concentrates in the above examples were successful in producing
black appearing colored optical fibers. The above example fibers were
found to have a complete cure of the primary and secondary coatings, and
were completely compatible with a fusion splicing device, resulting in
less than 0.01 dB/km of attenuation after splicing lengths of the example
fibers. The fibers produced had values of lightness (L), chroma (C) and
hue (H) to thereby produce the visual appearance of black and slate
meeting the requirements of the standards established by the Electronic
Industries Association, EIA/TIA-359-A entitled EIA Standard Colors for
Color Identification and Coding, January, 1985 and in EIA/TIA-598 entitled
Color Coding of Fiber Optic Cables, April 1992. Table II below provides
typical LCH values for the example fibers listed in Table I:
TABLE I
______________________________________
TYPICAL LCH VALUES
COLOR L C H
______________________________________
BROWNISH 0-35 0-20 320-360
BLACK
PURPLISH 0-35 0-20 300-340
BLACK
SLATE 35-80 0-10 60-140
______________________________________
Although the invention is described herein as utilizing a single secondary
coating, the invention will work equally as well with an optical fiber
having a plurality of secondary coatings. All that is required is that the
color concentrate be combined with the outermost secondary coating in
order to provide an optical fiber of the desired black appearing
coloration. Additionally, in an optical fiber having only a single,
primary coating, the pigment concentrate of the invention may be directly
combined with the primary coating in order to provide the desired black
appearing colored optical fiber.
Although the present invention has been described and illustrated with
respect to exemplary embodiments thereof, the foregoing the various other
additions and deletions may be made therein and thereto without departing
from the spirit and scope of the present invention.
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